I was never a big friend of manuals , i think that a well made tutorial and some mouse over help can cover everything .
Starting characters and failing is the best way to understand game mechanics , also it is the most fun way ( i am like in the 29th restart in Arcanum and i have used people's advice lol ).
The problem is with games that are made in a way that the character can not fail because the game stops to progress or it is simply too easy , this is what i call "casual".